If a container has a reducible volume, it may e.g. consist of a rigid outer container and of a flexible inner pouch which after discharge of container contents contracts each time accordingly, with pressure compensating openings being provided in the outer container for pressure compensation between the rigid outer container and the inner pouch. The container, however, may also be single-walled and e.g. have the shape of a tube which is compressed for discharging the material. Further examples of a container having a reducible volume are bellows-type containers, which gradually collapse upon discharge of the flowable material, and syringes the volume of which can be reduced by advancing a syringe plunger. It goes without saying that the above enumeration is only by way of example and not complete.
If the container is not of a reducible volume, volume compensation may also be achieved during discharge of the container contents through inflowing air which should then flow through a sterile filter.
The flowable contents of the container may be liquid and then be discharged in liquid form or as a spray, or it may be a suspension, cream, gel, ointment, or another substance, optionally of high viscosity.
A one-way valve device comprising an outer cap which is seated on the container neck and has an exit opening discharges the contents of the container in partial amounts, and the discharge in doses may be distributed over a prolonged period of time.
With many applications, it is important that the filling material remaining in the container should not be impaired by contamination, for instance by microorganisms or inorganic or organic impurities. Above all in pharmaceutical materials, but also e.g. in the case of cosmetic container contents, this determines the quality and is e.g. also applicable to flowable substances to be counted among foodstuff. That is why the material volume discharged from the container must not be compensated by (unfiltered) air entering into the container if a situation is to be prevented where bacteria, dust, moisture, oxygen etc. get into contact with the remaining contents of the container. That is why in the container of the preferred type the volume must be reduced in proportion to the amount of material discharged. It must above all be ensured that no microorganisms penetrate through the container opening and contaminate the remaining contents of the container.
Of course, it is also important to ensure that no contents of the container exits independently, for example during transportation of the container.